1. Field Of The Invention
This invention relates to a scroll type compressor, and more particularly, to an axial sealing mechanism for the scroll members of a scroll type compressor.
2. Description Of The Prior Art
A conventional scroll type compressor with an axial sealing mechanism for axially sealing the scroll members is illustrated in FIG. 1. The axial sealing mechanism shown in FIG. 1 is similar to the axial sealing mechanism described in U.S. Pat. No. 4,475,874. The scroll type compressor includes fixed scroll 10 having circular end plate 11 from which spiral element 12 extends, and orbiting scroll 20 having circular end plate 21 from which spiral element 22 extends. Block member 30 is attached to circular end plate 11 by a plurality of fastening members, such as bolts 31, to define chamber 40 in which orbiting scroll 20 is disposed. Spiral elements 12 and 22 are interfitted at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off pockets. Driving mechanism 50, which includes rotatably supported drive shaft 51, is connected to orbiting scroll 20 to effect the orbital motion of orbiting scroll 20. Oldham coupling 60 is disposed between circular end plate 21 and block member 30 to prevent the rotation of orbiting scroll 20 during its orbital motion.
Circular end plate 21 of orbiting scroll 20 divides chamber 40 into first chamber 41 in which spiral elements 12 and 22 are disposed and second chamber 42 in which Oldham coupling 60 and one end of driving mechanism 50 are disposed. Discharge port 70 is formed at a central portion of circular end plate 11 to discharge the compressed fluid from a central fluid pocket. Suction port 80 is formed at a peripheral portion of circular end plate 11 to supply suction fluid to the outermost fluid pockets. A pair of apertures 90 which are sized to produce a pressure throttling effect are formed at a middle portion of circular end plate 21 of orbiting scroll 20 to link second chamber 42 to a pair of intermediately compressed fluid pockets 41a.
During operation of the compressor, since the pressure in intermediate fluid pockets 41a facing aperture 90 fluctuates within a defined range, thus, even in a stable operating condition of the compressor, the pressure in second chamber 42, which is connected with intermediate fluid pockets 41a by apertures 90, is an average pressure which is related to the range of pressures in intermediate fluid pockets 41a. Accordingly, the axial sealing force applied against orbiting scroll 20 to urge it against fixed scroll 10 is a function of the average intermediate pressure in second chamber 42.
One of the disadvantages of the above prior art axial sealing mechanism is that, since second chamber 42 admits the intermediately compressed fluid from intermediate fluid pocket 41a in which pressure fluctuates within a range of pressures, the pressure in second chamber 42 also fluctuates thereby varying the axial sealing force applied to the orbiting scroll. This occurs even in the stable operating condition of the compressor. As a result, Oldham coupling 60 and driving mechanism 50 intermittently receive an undesirable thrust force which is generated by the reaction force to the compressed fluid in all the fluid pockets. This reduces the durability of the compressor.
Another disadvantage of the above prior art axial sealing mechanism is that the machining process for forming aperture 90 in circular end plate 21 must be very precise, which increases manufacturing cost and may lead to reduced operating efficiency in the event precise tolerances are not observed.